1. Field of the Invention
This invention relates to a semiconductor-laser-pumped solid-state laser and, more particularly, to a semiconductor-laser-pumped solid-state laser capable of generating a plurality of beams of laser light.
2. Description of the Related Art
FIG. 19 and 20 are a schematic plan view and a schematic side view of a semiconductor-laser-pumped solid-state laser apparatus in which a semiconductor laser element is disposed close to a laser medium having a small sectional area, and which is known, for example, as one described in "Laser Kenkyu" Vol. 18, No. 8 (1990) pp. 622-627. In the semiconductor-laser--pumped solid-state laser apparatus shown in FIGS. 19 and 20, a semiconductor laser device 1 generates pump light 2 which enters a solid state laser medium 3. For example, the solid state laser medium 3 is formed of a Nd:YAG (Y.sub.3-x Nd.sub.x Al.sub.5 O.sub.12) crystal having a length of 5 mm, a width of 2 mm and a thickness of 0.5 mm and having a rectangular cross-section. A coating which is nonreflective with respect to pump light 2 but is totally reflective with respect to laser light 4 is formed on a pump light incidence end surface 3a of the solid state laser medium 3, while a coating which is non-reflective with respect to laser light 4 is formed on an end surface 3b of the solid state laser medium 3. A partial reflection mirror 5 is disposed so as to face the end surface 3b of the solid state laser medium 3.
The operation of this semiconductor-laser-pumped solid-state laser apparatus will be described below. Pump light 2 enters the solid state laser medium 3 through the pump light incidence end surface 3a. Pump light 2 in the perpendicular direction is repeatedly reflected by upper and lower surfaces 3c of the solid state laser medium 3 and is absorbed by the solid state laser medium 3 while being confined in this medium. The solid state laser medium 3 is thereby pumped effectively. In the meantime, there is no need to confine the pump light 2 in the parallel direction because the beam divergence in this direction is comparatively small. Light spreading out perpendicularly to the semiconductor laser active layer is reflected by the upper and lower surfaces 3c, so that the light pump region in the solid laser medium 3 has a size of about 0.5 mm in each of the perpendicular and parallel directions with respect to the semiconductor laser active layer. A stable laser resonator is formed by the pump light incidence end surface 3a and the partial reflection mirror 5. For example, if the pump light incidence surface 3 a is flat, the radius of curvature of the partial reflection mirror 5 is 2500 mm, and the length of the resonator is 10 mm, then a beam of laser light 4 having a diameter of about 0.35 mm in a fundamental mode (Gaussian mode) is oscillated.
In the conventional semiconductor-laser-pumped solid-state laser apparatus, however, only one laser beam can be obtained from one laser device, and it is necessary to prepare a plurality of laser devices if a plurality of independent laser beams are required.